1. Field of the Invention
The present invention relates to a method of manufacturing an organic light emitting device and vapor deposition system.
2. Description of the Related Art
An organic light emitting device is generally formed of a laminated structure including a substrate, an anode, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode. In order to make lower the voltage of such an organic light emitting device, it is important to improve electron injectability from the cathode. More specifically, in order to improve electron injection efficiency, a metal, a metal compound, a metal salt, or the like having a low work function is used as a dopant. An organic layer containing such a dopant is used as the electron injection layer, and the dopant functions as a donor (electron donative) dopant.
In an organic film of the electron injection layer, a metal having a low work function donates electrons to put organic molecules in a radical anion state. This makes it possible for adjoining molecules to donate or accept electrons smoothly, and an injection barrier from the cathode is lowered to improve the electron injectability. Further, electron transportability by a hopping mechanism in the organic layer can also be improved.
Japanese Patent Application Laid-Open Nos. 2000-182774, 2004-311403, and 2005-123094 disclose lowering of an electron injection barrier by forming an electron injection layer so as to contain a metal compound and reducing the metal compound in the electron injection layer.
However, according to the technology disclosed in Japanese Patent Application Laid-Open Nos. 2000-182774, 2004-311403, and 2005-123094, when the metal compound is not reduced and remains in an organic film, it does not sufficiently function as a donor dopant, and even if a doping concentration is improved, drive voltage is not lowered. On the contrary, there is a possibility that the drive voltage may rise.